Antilock Brake System (North America)

DTC C0161 (North America)

Circuit Description

When the brake pedal is depressed, the contacts on the brake light switch close to illuminate the brake lights. Battery voltage is also applied to terminal 16 of the electronic brake control module (EBCM), which signals the antilock brake system (ABS) controller that the brakes are applied and ABS may be needed. Without this, signals from a wheel speed sensor that may indicate a need for ABS intervention are questionable. When the brake pedal is not depressed, the EBCM terminal 16 is grounded through the brake lights.

This procedure will check whether there is no output or constant output from the brake light switch and will determine the cause as a faulty switch or a problem in the circuitry.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0161 Stop Lamp Switch Circuit Open

Conditions for Running the DTC

* Vehicle speed is greater than 6 km/h (4 mph) with the brake pedal not applied
or
* Vehicle speed is greater than 15 km/h (9 mph) and the brake pedal is actuated.

Conditions for Setting the DTC

* The ground connection or the positive connection at the EBCM has failed.
* There is an open, short to ground, or short to positive in the vehicle wiring.
* The brake light switch has failed.

Action Taken When the DTC Sets

The system records a DTC C0161. The ABS and EBD operation is enabled and the ABS/EBD warning lamp doesn't turn ON.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Diagnostic Aids

Inspect wiring and connectors carefully and thoroughly. Failure to do so could result in misdiagnosis, causing part replacement with reappearance of the malfunction.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. This simple test will isolate the problem to the fuse-brake light switch-splice 301 area or the splice 301-EBCM area.
4. This is the 1st step in identifying an open, a short to ground, a short to voltage, or a faulty brake light switch.
12. This step begins the process of finding an open, a defective connector, or a faulty EBCM.